1. Field of the Invention
The present invention relates to a catalytic cracking catalyst comprising zeolite and a production process for olefin and a fuel oil using the same, specifically to a catalytic cracking catalyst comprising pentasil type zeolite modified with a rare earth element and zirconium and faujasite type zeolite and a process for catalytically cracking a heavy oil (containing 50% or more of a hydrocarbon fraction having a boiling point of 180° C. or higher) by using the above catalytic cracking catalyst to produce olefins (particularly propylene) and a fuel oil.
2. Description of the Related Art
Light olefins, particularly propylene are an important material as a basic raw material for various chemical products. A process in which light hydrocarbon such as butane and naphtha is used as a raw material and cracked in a tubular furnace of an external heating type by heating under steam atmosphere has so far widely been carried out as a production process for light olefins. However, the above process has the economically disadvantageous points that a high temperature of 800° C. or higher is required in order to enhance an olefin yield and that this makes it inevitable to use expensive apparatus materials. Further, carried out as well is a process in which olefins such as propylene are produced as by-products together with a fuel oil from a heavy oily by fluid catalytic cracking (hereinafter abbreviated as FCC) using a zeolite catalyst. However, the problem that light paraffins having a low value are produced in larger quantities is involved therein.
A process in which a hydrocarbon fraction is catalytically cracked using a catalyst comprising Y type zeolite and pentasil type zeolite containing phosphorus, magnesium and the like to produce light olefins is disclosed in patent document 1. Examples in which a hydrocarbon fraction having a distillation range of 229 to 340° C. is catalytically cracked to produce olefins having 2 to 4 carbon atoms in a proportion of 13 to 14 mass % are described in the examples (Table 2) of the above document. In this case, however, “cracking gas” accounts for about 27 mass %, and light paraffins having a low value which are obtained by deducting an amount of olefins having 2 to 4 carbon atoms from a “cracking gas” amount are produced in as large proportion as 13 to 14 mass %.
A process in which a hydrocarbon fraction is catalytically cracked using a catalyst comprising phosphorus and rare earth-containing zeolite of a high silica content having a pentasil structure and Y type zeolite to produce light olefins is disclosed in patent document 2. Examples in which a hydrocarbon fraction having a distillation range of 243 to 507° C. is catalytically cracked to produce olefins having 2 to 4 carbon atoms in a proportion of 37.1 mass % (ethylene: 5.32 mass %, propylene: 18.31 mass %, butenes: 13.47 mass %) are described in the examples (Table 4) of the above document. In this case, “cracking gas” accounts for 49.24 mass %, and it can be found that light paraffins having a low value which are obtained by deducting an amount of olefins having 2 to 4 carbon atoms from a “cracking gas” amount are produced in a proportion of 12.14 mass %.
A process in which a hydrocarbon fraction is catalytically cracked using a catalyst comprising high silica content zeolite containing a specific amount of a rare earth element and Y type zeolites (REY, high silica Y) to produce gasoline and light olefins is disclosed in patent document 3. An example in which hydrocarbon having a boiling point of 291° C. or higher is catalytically cracked to produce 8.6 mass % of propylene and 7.28 mass % of butenes is described in the example (Table 6, Example 1) of the above document. However, a production amount of propane is 3.03 mass %, and a production amount of butanes is 10.11 mass %. Thus, a production amount of light paraffins having a low value is large as well.
Further, known as well is a catalytic cracking process which is carried out using an ordinary FCC catalyst mixed with a catalyst containing ZSM-5 type zeolite as an additive for producing olefins. A catalytic cracking process in which a physical mixture of Y type zeolite and ZSM-5 type zeolite is used as a catalyst is disclosed in patent document 4. An example in which vacuum gas oil (VGO) is catalytically cracked to produce 17.8 mass % of propylene and 13.8 mass % of butenes is described in the examples (Table 2) of the above document. However, paraffins having 2 to 4 carbon atoms account for 14.6 mass %, and a lot of light paraffins is produced.
Results obtained by catalytically cracking a heavy oil with a commercial FCC catalyst mixed with an additive containing ZSM-5 are disclosed in non-patent document 1. The production amounts of propylene and butene are 6% and 5.8% respectively (11.8% in total), and a production amount of light paraffins (dry gas+LPG−propylene−butene) other than the above is 6.2%. Thus, a production proportion (light paraffins/(dry gas+LPG)) is as high as about 34%.
An example in which butane is cracked by using pentasil type zeolite modified with a rare earth element and zirconium to produce 14 to 22 mass % of propylene is disclosed in patent document 5. However, light hydrocarbons such as butane and naphtha are assumed as the raw material, and applicability thereof to a heavy oil is not described.
Further, processes in which a heavy oil is catalytically cracked by using a fluidized bed reactor of a down flow type to produce olefin and a fuel oil are disclosed (patent documents 6, 7 and 8). However, such a large amount of a catalyst that a catalyst/raw material oil ratio (C/O ratio) is 20 to 40 is required, and an amount of light paraffins is still large (patent document 8, Table 2: propylene/propane ratio=10.5).
As described above, the existing situation is that a catalyst which inhibits light paraffins having a low value from being produced to effectively produce olefins in catalytic cracking of heavy hydrocarbons has not yet been found.    Patent document 1: Japanese Patent Application Laid-Open No. 192431/1999    Patent document 2: Japanese Patent Application Laid-Open (through PCT) No. 504817/1997    Patent document 3: U.S. Pat. No. 5,358,918    Patent document 4: Japanese Patent Application Laid-Open No. 220466/1994    Patent document 5: Japanese Patent Application Laid-Open No. 143373/2004    Patent document 6: Japanese Patent Application Laid-Open No. 60453/1998    Patent document 7: Japanese Patent Application Laid-Open No. 241764/2002    Patent document 8: Japanese Patent Application Laid-Open No. 29620/2005    Non-patent document 1: Shokubai-Kasei-Gihou, Vol. 17, p. 15 to 24, 2000